The role of house flies (Musca Domestica) in transmission of avian influenza virus Subtype H5N1

Abstract

The objective of this study was to determine the potential role of the house flies in harboring and transmission avian influenza virus H5N1 (AIVs). To achieve this goal, this study was divided into three parts. The purpose of the first part was to determine the potential of the house flies as a vector of AIVs. In this part, the laboratory reared flies were experimentally fed with mixture containing the AIVs and then the external body surface of exposed flies was washed and sterile prior to preparation of homogenate whole fly between whole fly and brain heart infusion broth (BHI). The homogenate was inoculated into 10-day-old embryonated chicken eggs. Allantoic fluids were collected for determining virus concentration by HA test, RT-PCR assay. Moreover, the minimum of the house flies carrying AIVs was examined by inoculating one house fly homogenate into 10-day-old embryonated chicken eggs. In addition, the duration time of AIVs survival in house flies was determined by collecting exposed flies at different times of post exposure. The results in this part revealed that the house flies could carry the AIVs, one house fly was sufficient to carry and able to kill embryonated chicken eggs and the AIVs could survive within house flies for up to 96 hr. However, the virus titers were decreased over time. The second part that was the competence of the house flies as a transmission vector of AIVs in chickens under laboratory condition was determined. Three groups of 32-day-old chickens were individually inoculated AIVs infected house fly homogenate via oral route except the chickens in group 1 were inoculated with BHI, serving as a negative control group. Oropharyngeal and cloacal swabs were collected. Clinical signs and mortality were observed for 14 days post-inoculation (DPI). The experiment was terminated on 14 DPI and the tissues samples were collected for histopathological and immunohistochemistry evaluations. The results of this part indicated that AIVs infected house fly homogenate could induce the clinical signs and mortalities in inoculated chickens. Finally, the objective of last part was to examine the presence of the AIVs naturally infected house flies in epidemic area in Thailand during 2008. The result of this part revealed that none of AIVs naturally infected house flies was found. Nevertheless, all of the results in this study were conceivable illustrated to suggest that the house flies served as a mechanical vector of the AIVs and could transfer AIVs to chickens under experimental condition.